The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Internal combustion engines generate exhaust gas, including hydrocarbon (HC), carbon monoxide (CO), oxides of nitrogen (NOx), particulate matter (PM) and other emissions gases. An exhaust gas recirculation (EGR) system can be employed to reduce oxides of nitrogen (NOx) by diluting incoming air with recirculated exhaust gases which are inert, thus reducing peak combustion temperatures and correspondingly reducing NOx levels.
Combustion temperatures can be further reduced by cooling the recirculated exhaust gas, resulting in higher density recirculated exhaust gas. An EGR system can include a heat exchanger that cools the recirculating exhaust gas prior to entrance into the intake manifold. An EGR valve or other metering device may regulate the flow of the exhaust gas into the intake manifold.
A heat exchanger for use with an EGR system includes a plurality of heat exchange conduits constructed from thermally conductive material through which recirculating exhaust gas flows. The heat exchange conduits are in contact with a fluid, e.g., engine coolant or air that absorbs heat from the exhaust gas through the heat exchange conduit walls. Thermal efficiency, i.e., heat transfer through the heat exchange conduit walls may be reduced when hydrocarbons and soot including ash and particulate matter (PM) precipitates, coagulates and otherwise deposits onto and adheres to the walls of the heat exchange conduits.
Design of a heat exchanger for an EGR system can include compensating for loss of thermal efficiency during its service life, including sizing the heat exchanger with excess heat transfer capacity to compensate for fouling that can occur during its service life. This excess heat transfer capacity can consume available packaging space, add weight, and affect overall design of the heat exchanger.